For the high-resolution spectrometry of charged particles it is desirable to produce highly monochromatic beams of charged particles, i.e., streams containing particles of precisely equal energy, insofar as possible. For this purpose dispersion elements on an electrostatic basis are being used, using mainly sphere or cylinder condensers. Cylinder condensers consist of two concentric cylinder segment surfaces; sphere condensers have two concentric sphere segment surfaces. As a rule, the surfaces extend over an angle of 127.degree..
Basically, it is true in all these apparatus that the relative resolution .DELTA.E/E.sub.o is a constant which depends on the special geometry. It follows from this that E.sub.o is to be kept as small as possible in order to achieve a high absolute resolution. Then, however, the intensity that is achievable is limited by the space charge.